Their idea was that the bright autumn colouration in trees is a warning signal to insects about investment in chemical defence. In the forthcoming issue of Ecology Letters, Hagen, Jakobsen and Folstad present the first empirical test of this autumn signalling hypothesis.
They show that in mountain birch, increasing degree of autumn colouration in September is associated with a reduction in leaf damage from insects the following season, indicating that the most autumn coloured trees might have been less exposed to egg-laying insects.
This result is consistent with the idea that bright autumn colouration is a warning signal directed towards insects in search of favourable hosts for their progeny.
Ecology Letters